Hydrometallurgical treatment of metal bearing materials, such as copper ores, concentrates, and other metal bearing materials, has been well established for many years. Typically, conventional hydrometallurgical processes for copper recovery involve leaching metal bearing materials with an acidic solution, either atmospherically or under conditions of elevated temperature and pressure. The resultant process stream—the pregnant leach solution—is recovered, and a processing step such as solution extraction is used to form a highly concentrated and relatively pure metal value containing aqueous phase. One or more metal values may then be electrowon from this aqueous phase.
Certain ores consume a relatively high amount of acid during acidic leaching. Thus, highly acid consuming ores have conventionally been more expensive to process through acidic leaching. Highly acid consuming copper containing ores include copper carbonates, such as azurite and malachite, among other types of minerals.
Certain ores and/or flotation tailings contain a mix of oxides and sulfides of one or more metals associated with highly acid consuming gangue materials such as carbonates. These mixed materials may be problematic in acid leaching because of the highly acid consuming nature of the gangue minerals and because sulfide minerals leach more slowly and less completely than oxide minerals, causing low metal recovery and plant design complications.
Accordingly, processes that allow for metal recovery from highly acid consuming ores without the need for acid leaching would be advantageous.